With the rapid social and economic development in our country, the urbanization drive speeds up with each passing year, and amounts of infrastructure construction have reached to an unprecedented scale. Owing to their good overall performances and relatively low costs, concrete products have been widely applied to such fields as civil engineering, hydraulic engineering, harbors, bridges and roads. However, while concrete techniques have been widely applied at present, and concrete strength has been improved, the drawbacks of high energy consumption, high carbon emissions and inadequate durability under harsh conditions existing in the concrete industry remain to be the major issues facing the world today. Therefore, how to effectively reduce energy consumption of concrete products and improve their rapid hardening, shrinkage resistance, cracking resistance and durability under harsh conditions has been the focus of current researches.
With the development of nanotechnology, recent years have seen rapid development on many researches on self-assembled micro-nano composite superstructured functional materials, and their applications may endow numerous traditional materials with superior overall synergistic performances. Through simple manipulation over their dimensions and geometry appearances, nano-particles are self-assembled as a one-dimensional, two-dimensional or three-dimensional ordered structure; thereafter, novel overall synergistic characteristics may be obtained. Moreover, interactions among nano-particles may be controlled to regulate their nature. Consequently, these newly-emerging novel micro-nano composite superstructured functional materials will have positive promotion effects on performance optimization of concrete.
Currently, micro-nano composite hollow microsphere superstructures, which have such advantages as low densities, high specific surface areas and good monodispersity, and can accommodate other materials in their hollow portions, have become the frontier and focus of research in nanometer material science, chemistry, physics and bioscience. In a hollow microsphere superstructure, the spherical shell of the hollow microsphere is comprised of nanorods/nanosheets arranged in a radial direction. Nano-sized “channels” are present among these nanorods/nanosheets, and these channels provide effective transmission ways for the exchange between hollow portions and external substances. When a micro-nano composite hollow superstructured material is combined with concrete, as hollow structures may store some moisture required by hydration of concrete, some of the water will be slowly released from the inside to the concrete along nano-sized “channels” on spherical shells of hollow spheres, thus changing the hydration process of cement concrete members. As such, conditions may be created for internal curing of cement concrete. Under the conditions of internal curing, the hydration degree of cement concrete will be improved, problems of early cracking will be alleviated, and strength and toughness of concrete will be enhanced.